The present invention relates to a signal processing device having a signal processing circuit electrically connected to a switching element and capable of supplying an anti-corrosion current to a contact point of the switching element, and a control unit having the same.
FIG. 1 is a circuit diagram illustrating an electrical circuit of a related-art control unit 11. An input terminal 13 of the control unit 11 is electrically connected to a switching element 14. An anti-corrosion current supplying resistance 15 for supplying an anti-corrosion current to the switching element 14 is connected in parallel between the switching element 14 and the input terminal 13 as a discrete component of an integrated circuit 12. In addition, the integrated circuit 12 is provided with a surge protection circuit 16 for absorbing a surge input to the input terminal 13, and a series resistor 18 for externally preventing the integrated circuit 12 from being destroyed by the surge is connected in series. Also, the integrated circuit 12 is provided with a contact logic determination section 17 for determining a contact logic of the switching element 14 on the basis of a voltage of the input terminal 13 (for example, refer to the Japanese Patent No. 2879807).
In the related-art, since the anti-corrosion current supplying resistance 15 is provided as a discrete component, the number of discrete components increases. Accordingly, in the control unit 10 including the integrated circuit 12 having a plurality of input channels, the total number of discrete components significantly increases (It is necessary to prepare the series resistor 18 as a discrete component because the surge input to the integrated circuit 12 should be externally avoided).